Fix scope issue in simd loops

The iteration variable being declared local raised errors
when using the simd macro twice in the same scope.

Also, it now behaves like normal for, i.e. if the iteration
variable was defined, its value is updated at the end of the loop.

Also, code cosmetics.

base/simdloop.jl

@@ -12,36 +12,28 @@ end
 # Parse iteration space expression
 # symbol '=' range
 # symbol 'in' range
-function parse_iteration_space( x )
- if !Meta.isexpr(x,[:(=),:in])
- throw( SimdError("= or in expected"))
- elseif length(x.args)!=2
- throw( SimdError("simd range syntax is wrong"))
- elseif !isa(x.args[1],Symbol)
- throw( SimdError("simd loop index must be a symbol"))
- else
- x.args # symbol, range
- end
+function parse_iteration_space(x)
+ Meta.isexpr(x, [:(=), :in]) || throw(SimdError("= or in expected"))
+ length(x.args) == 2 || throw(SimdError("simd range syntax is wrong"))
+ isa(x.args[1], Symbol) || throw(SimdError("simd loop index must be a symbol"))
+ x.args # symbol, range
 end
 
 # Compile Expr x in context of @simd.
 function compile(x)
- if !Meta.isexpr(x,:for)
- throw(SimdError("for loop expected"))
- elseif length(x.args)!=2
- throw(SimdError("1D for loop expected"))
- else
- var,range = parse_iteration_space(x.args[1])
- r = gensym() # Range
- n = gensym() # Trip count
- s = gensym() # Step
- i = gensym() # Index variable
- # LLVM vectorizer needs to compute a trip count, so make it obvious.
- quote
- local $r = $range
- local $n = length($r)
- local $s = step($r)
- local $var = first($r)
+ Meta.isexpr(x, :for) || throw(SimdError("for loop expected"))
+ length(x.args) == 2 || throw(SimdError("1D for loop expected"))
+
+ var,range = parse_iteration_space(x.args[1])
+ svar = Expr(:call, :symbol, string(var))
+ n = gensym("n") # Trip count
+ s = gensym("s") # Step
+ i = gensym("i") # Index variable
+ # LLVM vectorizer needs to compute a trip count, so make it obvious.
+ quote
+ let $var = first($range)
+ local $n = length($range)
+ local $s = step($range)
  local $i = zero($n)
  while $i < $n
  $(x.args[2])
@@ -50,11 +42,13 @@ function compile(x)
  $(Expr(:simdloop)) # Mark loop as SIMD loop
  end
  end
+ isdefined($svar) && ($var = last($range))
+ nothing
  end
 end
 
 macro simd(forloop)
  esc(compile(forloop))
 end
 
-end # simdloop
+end # module SimdLoop